1. Field of the Invention
The present invention relates to a method and apparatus for the automatic filling and packaging of foodstuffs under aseptic or low-bacterial count conditions, which foodstuffs have been previously disinfected or sterilized and then passed to a filling and packing plant. The packaging material is disinfected by means of high-intensity ultraviolet radiation.
2. Description of the Prior Art
Automatic techniques for the aseptic filling and packaging of foodstuffs is being used on an increasingly wide scale. To date, the aseptic packing of pre-sterilized (uperised) milk in packages made of a composite paper material has gained particularly wide acceptance. (The uperisation of milk is described, for example, in Industr. alim, agr. 1956, p. 635-640.) The packages are predominantly tetrahedral or rectangular in shape and are made up by applying transverse seals to a tube of packaging material formed from a strip of packaging material drawn from a roll (cf. TARA 271, February 1972, page 104).
Generally, "aseptic packing" can also be defined as the placing of a cold, commercially sterile foodstuff into a pre-sterilised container under sterile conditions. The container, if provided with an appropriately pre-sterilized lid is enclosed in a sterile environment so as to produce an airtight package (Food Technology, August 1972, page 70).
Another packaging technique which has become very important is the packaging of low-bacteria count foodstuffs in, for example, deep-drawn prefabricated beakers which are then heat-sealed with refined aluminum foil. Common applications include the packing of yoghourt, soured milk, cream, and so on. An essential feature of the known techniques is that no sterilization occurs of the contents by heating in the already sealed package, as is the case with canning and preserving techniques. The tedious heating process is thus eliminated without having to take into account deleterious changes in the contents of the packaged foodstuff such as flavour or composition. Furthermore, the packages can be made of materials, in particular plastics, which cannot withstand elevated temperatures. A particularly critical aspect of the known techniques is that the packaging material must be so free from bacteria as to provide the greatest possible safeguard against infection of the previously sterilized or disinfected contents by bacteria, moulds and/or yeasts which could cause spoiling. Here it is pertinent to note that in the case of uperised milk, for example, a single bacterium in the package can cause the milk to spoil.
A large variety of methods and apparatus for disinfecting packaging materials have been proposed and applied in practice. These are reviewed, for example, in "Verpackungs-Rundschau" 7 (1970) pages 51-54. Other references in the literature include Food Technology, September 1973, page 49 (disinfection with alcohol and ultraviolet radiation) and Food Technology, August 1972, pages 70-74 (e.g. disinfection with wet and high-temperature steam, the so-called "James Dole process"). In particular, a method is known as described in "Verpackungs-Rundschau" 7 (1970) page 52-53, whereby packaging material is disinfected by means of high-intensity ultraviolet radiation. It is disclosed that the ultraviolet wavelength of 254 nm has proven especially effective against all relevant micro-organisms. However, micro-organisms differ with regard to their sensitivity to ultraviolet radiation. Thorough destruction of all micro-organisms present can be achieved only with a very heavy radiation dose. On page 54, op. cit., it is disclosed that the high destruction rates are obtained only when the distance of the foodstuff from the light source is very short. Further, it is not known whether or how packages can be sterilized to the required degree and at a sufficient speed as required in filling plant operations.
A need therefore continues to exist for a method of packaging foodstuffs under sterile conditions by exposure of the packing material to a sterilizing light source such that the degree of sterilization is swift and complete.